1. Technical Field
Aspects of the present invention relate to low-pressure and high-pressure ion mobility spectrometers.
2. Related Art
Ionized large molecules are analyzed in mass spectrometers and in ion mobility spectrometers. In related art, mass spectrometers molecule ions are analyzed by determining their deflections in electromagnetic fields to determine their molecule weight, which is approximately proportional to the volume of a molecule under investigation. Ion mobility spectrometers molecule ions are analyzed by determining their velocities, v=K*E, when they are dragged through a buffer gas by an electric field “E” and so their mobilities “K” are approximately proportional to their cross sections.
Ion mobility spectrometers require that the molecule ions to be investigated are entered as short clouds. What are the measured are then the times these clouds need to pass through the length of an ion mobility spectrometer, as is disclosed in G. A. Eiceman and Z. Karpas in “Ion Mobility Spectrometry” 2. ed. Boca Raton, Fla., 2005. What are very important in such ion mobility spectrometers are the used ion gates that form these ion clouds from a continuous ion beam. Such ion gates are for instance disclosed in: A. M. Thyndal, C. F. Powel Proc. Royal Soc. of London 129 (809), (1930) 162 and N. E. Bradbury, R. A. Nielsen, Phys. Rev. 49 (5), (1936) 388. Both of these ion gates consist of harp-like grids placed perpendicular to the incoming ion beam that allow passage of ions only during short time intervals during which the wires of these grids are all at the same potential. At all other times, no ions can pass since different potentials are applied to neighboring wires, in which case the ions are attracted to one of these wires and are so kept from propagating forward in said ion mobility spectrometer.
Related art investigations of molecules have become important in applications for environmental, biological, medical, and pharmacological problems. These related art techniques allow characterization of a molecule not by weight as in a mass spectrometer but by cross section, and thus, by structure since the cross section of a long molecule is certainly bigger when it is stretched out as when it is coiled up. Such characterizations are especially important for the investigation of molecule fragments into which a large molecule breaks up when it absorbs energy, for example, from collisions with buffer gas molecules or atoms.